Means for protecting switch-contacts under oil



H. F. STRATTON- MEANS FOR PROTECTING SWITCH CONTACTS UNDER OIL.

APPLICATION FILED NOV.12, 1919.

Patented July 5, 1921. V

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To all whom'it may concern? 7 M Be itknown that 1,: HARRY F.' S'rnA'r'roN, a' citizen of the United States; residing at Cleveland, in the county of'Ouyahoga and State of Ohio, have invented new anduseful Improvements in Means for 'Protecting Switch-Contacts Under Oil, of which the following is a specification. I v My invention relates to "means for tectingiswitch-contacts under oil.

Butt sliding, or rolling copper contacts are much used for making and breaking heavy electric currents in airf Whensuch switches operate in air-part o'fithe wear of their contacting surfaces is due to friction during closing, but most of'itcaused probablywby the arcing during opening, at which time little globules of copper are formedon thecontactss: These globules are detached either by the force of the are or by pas y the rubbing of the contacts together. Nev

ertheless, the life of such contacts in air is very great. Although beneficial results have been secured by using butt-contactsin oil, thishas been-effected at the expense of a decreased operating life of the contacts; (lontrary to the case of contacts in air,- the heaviest depreciation of contacts in oil oc curs during theirclosing operation. As the fiatsurfaces of the contacts are approaching each other, they finally touch at some'point, the remaining parts of the contact-surfaces beingseparated by a thin film of oil. At the said point there occurs immediately a very high current density which causes incipient fusion of the copper, and high heating and semi-explosive action of the oil film. Little globules of copper are thrown out sidewise and the entire contacting surfaces become roughened, so that, as the contacts move, one on another, portions of "the copper are worn ofl more rapidly than in the case of contacts opening in air. It is the principal object of this invention to prolongthe life of contacts operating under oil. ThisI accomplish by providing means whereby some or all of the contacts in oil may be closed before allowing current to pass through them. By so doing the oil film'between the contacts is well squeezed out before the current flows, and, as contact has been made at a number of points, no great heating occurs when current begins to flow, and there is not much burning of the oil. Not only is the life of 3 Specificationof mar-S mam.

Application meamvemm 12, 1919." Serial No.

' the winding :5 is' energized.

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Patented nly 337,591. l

the contacts greatly increasedif they are closed in oil before current flows through them, but their life is also increasedby the stoppage ,of the current before ..they are opened; My invention isparticularly advantageous in systems where 1t'1s required to d1sconnecttwo or more lines from a transformer or an equivalent device;

: Referring to the accompanyingdrawings, they .show one embodiment'of myv invention, the parts thereof being shown in th ree different positions in the three figures.

' source ofcurrent supply or from an auto 4 Figure 1 is'a diagrammatic view showin'g 1 thefswitch. H p Fig 2 isia similar. View showing the switch partly closed:

-Fig; .3 1 shows the switch any closed. 1

" On Fig. 1 of' the drawings, 1 designates a tank containing oil, the level thereof, being indicatedat 2.

Withinthe tank land below the oil level i 2 is the frame 3 to which the U-shaped core l is secured. On thelower legof the core is the winding 5; 6 is the armatureadapted to engage thepoles 7 and-8 of the core 4 when is pivoted-to the frame 3 at 1 8O 1 The armature The. switch lever 11 is pivoted between its ends at 12, one end being pivoted toiithe armature at 13 and' the other end carrying the. contacts lt-and 15 insu1at'ed from each other. I

15' is asecond switch lever pivoted at one end to the frame at 16. The link 17 connects the pivot 13 to an intermediate point 18 of the lever 15. The free end of the lever 15' has the contact 19 adapted to engage with the yielding contact 20. The con tacts 21 and 22 areengaged, respectively, by

the contacts 14 and 15 and are connected to the supply lines 28 and 29 and the contact 19 is connected to the supply line 30. The contacts 14, 15, and 20 are connected, re spectively, to the motor leads 23, 24, and 25 of the alternating motor M, having the stator windings 26 and the rotor'27.

The lines 28, 29 and 30 having been connected to a suitable source of alternating current and the winding5 having been supplied with current when the parts are as in Fig. 1, the armature 6 movesthrough the position shown in Fi 2, at which position the link 17 has broug t the contacts 19 and through the positions shownon Fig. 2, they reach the positions shown on Fig. 3 in which the contacts 14, 21 and 15,22 are closed,

and the motor leads 23, 24, and 25 are connected to the supply lines 28, 29, and 30..

The spring back of the contact 20 permits the link 17, the armature 6, and the levers 11 and 15 to travel past the positions shown in Fig. 2 to those shown in Fig. 3', in which the contacts 14 and 15 have caused the compression of'the springsbehi-nd the contacts 21 and 22.: When the winding 5 is deenergized the parts all drop back to the positions shown in Fig. 1, passing through the position shown in Fig.2 where the contacts 14:, 21 and 15, 22- are open while the contacts 19 and 20 are still closed.

Itis not essential so far asthis invention is concerned that all the contacts be under oil. While it is preferred in practice to have all the contacts under oil, my invention could be used if only one pair of con tacts, the ones first to close or the last to open, are in oil. The contacts- 19 and 20 might readily be made to close last and? open first if desired, merely by changing the length of the link. 17 and the position of the pivot 12.

While the opening of onlythe contacts 1 1, 21 and 15,22 disconnects the motor from the source of supply, there remains the danger that the wires connected to the contacts 19 and 20' may become grounded and severely shock or injure persons touching any of those wires. Insurance-companies require that all the line and transformer swltches be opened upon cutting the current supply from the motor. By closing some of the switches first there is economy of power and of structure. The switch closingv magnet is small and too much work is required of it to close all the switches simultaneously.

The principles of my invention may ob- "viously be" applied to systems other than that shown. To make the drawing simpler, the, motor is shown connected to the lines without'the' interposition of a. transformer, but the principles of this invention are obviously applicable to a motor" system employing transformers. In fact, this invention is applicable whenever a plurality of connections between a translating device and a source of current supply, whatever its nature, are either preferably or necessarily made and opened.

I claim:

'1. In a circuit controller for multiple c0nductors, a tank, oil therein, ,switclrcontacts for each conductor, some at least of said contacts bein submerged in the: oil, and means where y all the contacts may be closed and whereby some of the submerged contacts close before the remaining contacts close, and whereby some of the submerged contacts may be opened only after the remaining contactsha-ve been opened.

2. In a circuit controller for multiple conductors, a tank,,oiil therein, a switch for each conductor, at least oneof the: switches being submerged in-the oil, and means for closing all the switches, and for closing some of the submerged switches before the remaining. switches may he closed.

3. In a circuitcontroller for multiple conductors, a tank, oil therein, aswitchin each line, at least one of the switches. being submerged in the oil, and means for closing allthe switches, and for opening some. of the submerged switches only after the remaining switches have been opened.

Signed at Cleveland, Ohio, this 5th day of November, 1919.

HARRY F. STRATTON. 

